The present invention relates to a local connection of sheets onto one another and a method and apparatus for the implementation thereof. In particular, the invention is applied to the connection of a top and a bottom sheet onto one another at their common contact surface and in at least one defined connection zone. Sheets here mean relatively thin pieces of material that are thus (somewhat elastically) pliable, but possess a certain rigidity, for example sheets (boards) based on cardboard, plastic or laminates.
Currently connecting such sheets to one another is generally done by gluing or stapling the sheets together in the connection zone, attaching them together with rivets, joining them with binding wire (for example by stitching), fusing, etc. These techniques are applied to the cover flaps of packaging boxes, for example. To this end, a foreign material is generally used that has a composition which is different from the raw material of the sheets themselves. When recycling the worn sheets or objects manufactured from them, such as receptacles, this foreign material often constitutes an ecological difficulty. Indeed, the foreign material can impermissibly contaminate the sheet with regard to its subsequent processing in recycling lines (by shredding or grinding) or for the reuse of the ground raw material.
It is known from EP 169499 that a cardboard packaging box can be closed by locally connecting together the cover flaps lying on one another, without the addition of foreign material. To this end, a suitable opening is first made in the bottom cover flap. This intervention necessarily produces pieces of waste from the bottom sheet. Then suitable pre-cut connecting lips are pressed in the top cover flap transversely through the opening below two tongues of the bottom cover flap that border this opening. With this construction, however, the opening still exists after the connecting operation. Furthermore, the prior separate cutting operations in the bottom and top sheet are done completely separately from the subsequent actual connecting operation with a separate pressing apparatus.